I could be wrong, but I assumed people don't generally pay much attention to profiles. I focus on the request threads.
But some basics to include wherever you post it:
- Gender info (yours, what you're looking to play opposite, etc.)
- Where you want to RP (threads, PMs, Discord, etc)
- What you're into/looking for, or perhaps an F-list.
- What kind of posting frequency you offer/expect. Daily? Weekly?